Medical probes have the ability to provide images from inside the patient's body. Considering the potential damage to a human body caused by the insertion of a foreign object, it is preferable for the probe to be as small as possible. Additionally, the ability to image within small pathways such as small vessels, small ducts, small needles, cracks etc., requires a small probe size.
One useful medical probe employs a spectrally encoded endoscopy (“SEE”), which is a miniature endoscopy technology that can conduct high-definition imaging through a mm or sub-mm diameter probe. With SEE, broadband light is diffracted by a grating at the tip of the fiber, producing a dispersed spectrum on the sample. Light returned from the sample is detected using a spectrometer; and each resolvable wavelength corresponds to reflectance from a different point on the sample. In the SEE probe, illumination or/and detection fiber is oscillated or rotated so that illumination/detection area is scanned the rotating spectrally-encoded line.
The principle of the SEE technique and an SEE probe with a diameter of 0.5 mm, i.e., 500 μm have been described in D. Yelin et al., Nature Vol. 443, 765-765 (2006). SEE can produce high-quality images in two- and three-dimensions. SEE probes that image the location in front of the probes have been demonstrated using a 350-μm diameter probe, which produced high-quality images in two- and three-dimensions. See, for example, A Zeidan et al., Optics Letters Vol. 39, Issue 16, pp. 4871-4874 (2014). Zeidan proposes using an optical fiber rotary junction between probe and console (light source or spectrometer) to obtain 360-degree probe rotation.
Similarly, WO 2015/116951 disclosed a forward view SEE, illumination fiber where the fiber and dispersion optics are rotated using a rotary junction. This application is herein incorporated by reference in its entirety. Additional disclosure of SEE probes includes U.S. Pat. No. 8,818,149, which disclosed spectrally encoded endoscopy techniques and apparatus and U.S. Pat. Pub. 2011/0275899, which disclosed a spectrally encoded miniature endoscopic imaging probe. While the rotation of the optical head is discussed for larger probes, for at least narrow vessels, a special rotating junction must be used.
Each of these probes provides a rotary junction for connecting the rotating illumination or detection optics to a non-rotating portion of the fiber. In order to obtain high resolution, it is preferable to use either single-mode fiber (SMF) or small core multi-mode fiber (MMF). Typical core diameters for the MMF is less than 50 μm, for example 5 or 10 μm. Thus, when the probe is connected to a rotary junction in order to allow for rotational motion, the fibers must be carefully coupled to the rotary junction. Light coupling of rotary joint with such fibers is particularly challenging. The coupling efficiency is low, usually less than 50% in the case of SMF-SMF coupling. Additionally, the efficiency fluctuates along the rotation.
Thus, there is need for a new SEE probe and apparatus that does not need the added expense and complication of a rotary junction but allows for scanning of the illumination and/or detection portion